1. Field of the Invention
This invention relates generally to pumps, and more particulaly to pumps powered by expansion of a gas and/or steam
This invention relates to improvements of an existing patent described in U.S. Pat. No. 4,469,472, of Newby.
2. Description of Prior Art
One of the first of many devices that used the power of expanding gas was built by Hero of Alexandria in the first century of the Christian era. He invented a solar siphon that could transfer water from one container to another when it was placed in the sun. Solar energy heated air inside a sealed chamber; the heated air expanded and exerted pressure on the water inside the chamber, forcing it out
In the mid-nineteenth century, Mouchot designed a solar pump including a sealed, copper cylinder partially filled with water, and a parabolic reflector for focusing sunlight on the cylinder. As the air expanded the water was forced from the cylinder through a one way check valve. A more modem example of a solar pump is found in U.S. Pat. No. 3,972,651 of Fletcher. The pump includes a hermetically sealed enclosure floating on a reservoir of water. The enclosure includes a solar heated chamber and a cooling chamber that communicates through a plurality of heat sinks. At the bottom of the enclosure 11 there is a sump which is in communication with the reservoir of water via a one way valve. When the air in heated chamber expands it will flow through the heat sinks into the cooling chamber and exert pressure on the water in sump to force it up a conduit to an output flume. Flecher's device is metered by a tipple which is filled by dribbles of water from the flume. When the tipple is filled with water it will tip over, raising a `displacer` which separated the chambers and. This cools the air with in the enclosure and causes water to flow into the sump through valve. When the tipple empties the dispalcer falls and the cycle is repeated.
Flechers's device is an example of a closed system solar pump, that is, the same air is used over and over during the expansion and compression cycles and is never vented to the atmosphere. As such, Flecher's pump has many points of similarity with the Stirling hot air engine, which is a classic example of a closed system heat engine. A problem with a closed system pumps or engines is that their design is complicated by the need for complete pressure integrity, and by the elaborate heat dissipating mechanism required to cool the air between cycles. For example, most of the complexity in Flecher's device is found in the displacer and tipple mechanism which cools the air within the enclosure. Similarly, a Stirling hot air engine requires water jackets around the compression cylinder and/or an elaborate array of heat radiating fins.
A modem example of an open system pump is found in U.S. Pat. No. 4,469,472 of Newby. In FIGS. 5 and 6 of this patent a simplified version of an open system pump is shown. It is shown to include a hollow enclosure, a float disposed within the enclosure, and a flapper type check valve. The enclosure is provided with an upper orifice, a lower orifice and an output orifice. A check valve is coupled to an output pipe leading from the output orifice. An upper surface of float seats against upper orifice to seal the upper end of the enclosure Happer valve seals the lower orifice whenever the pressure within is greater than the water pressure outside of it. The operation of this embodiment is described as follows: As heat impinges the outer surface of enclosure the air within the enclosure expands and drives the water out of the enclosure. As the enclosure empties it will become more buoyant and will rise in the reservoir, and simultaneously the float will become less buoyant and will sink within the enclosure. When the upper orifice is unsealed, the hot, pressurized air within the enclosure will escape, and flapper valve will open to allow the enclosure to partially sink to its original or starting position.
The main question regarding the function of this design is the problem of maintaining a seal with the upper orifice. Air borne dust could easily corrupt the sealing surface of the orifice or, chemical corrosion from the water could corrode the float sealing surface. Either or both contaminates could make this device inoperable.
Another problem with this design (see FIG. 7 of U.S. Pat. No. 4,469,472) is that it can not function if the upper part of the chamber, that is, the part above the membrane, fills with fluid.